Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $57.74   7.339%   $61.9775   $61.98   $62.00   $62.00  
  Purchase #2 $88.74   3.774%   $92.089   $92.09   $92.10   $92.10  
  Purchase #3 $66.65   3.170%   $68.7628   $68.76   $68.75   $68.80  
  Purchase #4 $92.91   11.106%   $103.2286   $103.23   $103.25   $103.20  
  Purchase #5 $216.38   6.200%   $229.7956   $229.80   $229.80   $229.80  
  Purchase #6 $248.83   9.211%   $271.7497   $271.75   $271.75   $271.70  
  Purchase #7 $167.39   5.486%   $176.573   $176.57   $176.55   $176.60  
  7 purchase totals = $938.64       $1,004.1762   $1,004.18   $1,004.20   $1,004.20